For me it's because nothing they have shown gives me the same vibe as Dishonored, Prey, or even Deathloop. You could swap another developer logo into the trailers for this game and I'd believe it.But They’ve released interview after interview where they’ve stated the game is an Arkane game through and through, and will have the Arkane flair familiar to their fans, just in a much more ambitious package.
I guess the real question is why you don’t believe them.
Plus the whole loot system they are going with. I don't like tiered loot systems or looter shooters in general.
I love Arkane games and was excited for their next title and what I've seen so far has been very disappointing.